This invention relates generally to variable inlet guide vanes for gas turbine engines and more particularly to bushings and clock springs for such vanes.
Gas turbine engines often include airfoil-shaped inlet guide vanes for directing inlet flow to a downstream fan or compressor. In some applications the inlet guide vanes have a variable effective angle in order to throttle mass flow through the engine as needed in different operating conditions.
Portions of the engine near its forward end, including the inlet guide vanes, are subject to ice accretion in some flight conditions. This ice is typically removed by directing heated bypass air on or through the inlet guide vanes. Unfortunately, use of bleed air directly impacts engine efficiency and requires relatively heavy high-temperature pipes and valving.
It is known to use electrical heating for de-icing, for example using slip rings to transfer electrical current from a helicopter rotor head to the rotor blades. However, variable inlet guide vanes must react significant gas loads not present in other applications and thus must be firmly supported at their points of rotation, making delivery of electrical current more difficult. Furthermore, the guide vane bushings must be packed into a tight physical space.